Process of producing cement and products thereof.



ARTHUR C. SPENCER, OF WASHINGTON, DISTRICT OF COLUMBIA.

PROCESS OF PRODUCING CEMENT AND PRODUCTS THEREOF.

No Drawing.

To all whom it may concern:

Be it known that I, ARTHUR C. SPENCER, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in Processes of Producing Cement and Products Thereof, of which the following is a specification.

This invention relates to processes of producing cement and products thereof; and it comprises a method wherein certain zinc ore products, tailings or residues are submitted to a sintering or clinkering heat under conditlons favoring the evolution of residual zinc 1n fume form, and advantageously in a rotary kiln, and the evolved zinc compounds are recovered from the waste gases of the heating operation while the sintered residue is collected and ground for cement purposes; and it also comprises as a new composition of matter a clinkered or sintered substance possessing cementitious properties when powdered and having the composition of a clinkered zinc ore gangue containing traces of zinc; all as-more fully hereinafter set forth and as claimed.

Zinc'ores of the franklinite-willemite type such as are mined and dressed in New Jersey, may be generally described as containing mainly franklinite, willemite, tephroite, zinkite, a manganiferous calcite gangue, and varying amounts of fluorite, feldspar, hornblende, pyroxene, garnet, etc. A rather complicated system of dressing and concern trating these ores is now in use. The granules of ore may of course carry several minerals at once. Generally the ore is granulated and first passed through magnetic separators of different strengths. The first magnets are generally 'not so powerful as those later used and they remove mainly franklinite and granules rich in franklinite. The next and stronger magnets remove most of the residual franklinite together with some hornblende, garnet, etc., giving what is known as half-and-half. The residual mineral matter passing the magnets and including the calcite, willemite, zinkite, fluorite, feldspar, etc., is' then treated by jigs, shaking tables, buddles, etc., giving concentrates rich in heavy zinc minerals and tailings rich in manganiferous calcite but also containing some zinc minerals and silicates carrying alumina and iron.

The accumulated tailings around the dressing works carry over 5 per cent. of

Specification of Letters Patent.

Application filed April 13, 1911. Serial No. 620,833.

,evolution of zinc PatentedDec. 19, 1911.

zinc though reduce the amountthus lost to about 3 per cent. Most of the zinc is in the form of silicate or willemite though there is some ZnO replacing CaO in the calcite, as well as some franklinite carried by the calcite granules. These tailings are practically valuelss. I have discovered that when these tailings are calcined at a temperature Suflicient to expel the carbon dioxid of the calcite, there is an which passes away as fumiform oxid' with the carbon dioxid. This zinc apparently comes mainly from the manganiferous and zinkiferous calcite. The finer the comminution the greater is the amount of zinc evolved. If now the temperature be raised to the oint where the lime begins to combine witli the silica and silicates, that is, to a fritting, sintering, or clinkering temperature, there is a second and greater evolution of fumiform zinc oxid; probably from decomposition of the willemite and franklinite by lime. The iron of the franklinite combines with the lime, such FeO as is present quickly becoming peroxidized to Fe. .O.,.

The clinker resulting from heating'to a clinkering temperature I find to be valuable as a cement when fine ground, possessing eminently good hydraulic properties. It may still contain from traces up to one-half per cent. of zinc oxid, though by regulating the heat treatment the zinc' may be practically completely expelled. Its content of manganese is rather high. Probably this manganese functions in giving the cement hydraulic qualities.

The composition of thetailings as regards lime varies from day to day with the temporary ratio between gangue and ore in the material mined and treated, but the average composition is about right for cement puroses'and in handling accumulated tailings, by a little selection to secure an average material, good cement can be made. Where the material is used as produced, these daily variations can be corrected by the addition of small amounts of clay when the tailings run rich in gangue and low in silica and sesquioxid, or of limestone when the gangue is deficient. An addition of half-andhalf is also useful in correcting for high lime content; and such an addition enriches the zinc fume. This material may run between 20 and 30 per cent. of zinc oxld. It contains considerable silicates.

present practice is supposed to.

' good composition may be corrected, when neces- I maybe employeilgfor heating the material I with fume collecting means.

"The half-and-half may be submitted to the present operation in lieu of the-final ore.

tailingsasa good recovery of zinc and ,a cementitious clinker are obtained. Its

sary,'by the use of tailings of appropriate compositions Any suitable furnace or heating means to the clinkering temperature' if provided The fumiform zinc oxid being extremely fine, such means' calcining stage and that evolved in the should be eficients type of heating means,

Wetmethods of collection. may Joe employed; [or the waste gases may be cooled and passed through bag filters. The :heating may be performed. in the ordinaryfrotary inclined cement kiln. With such a" kiln both the zinc oxid evolved' in the clinkering stage join the products of combustion and pass forward together with the f dust incident to the operation of the kiln.

The waste-gases from the kiln may be passed through any ordinary form of fume collector, giving a mixture of calcareous dust and zinc oxid which may be treated as a zincore byqzoncentrating or smelting. 'Two-.

section kilns prov ded witlTi'ndividual firing means may be employed A to reduce the amountof barren kiln dustadmixed with the zinc oxid recovered, less dust being evolved from cement mixtureswhere the calcining and clinkering are not performed by the same flame. Stationary kilns may be employed with briqueted ore.

in lieu of sending the waste gases to a chimney stack they may first be directed through a cooler, such as vertical Ufl-shaped piping and then through zinc, it

bag filters, using a fan to secure draftthrough the kiln. In order to secure a maximum recovery of is advantageous to prolong the period of exposure to a clinkering heat as long as possible,

ture to prevent actual 'fusion as the latter would injure the cement and practically preclude further recovery of zinc. The amount bf zinc oxid evolved in a time unit is pro portional to the surface exposed. For this reason, also, the originally granular material isbest fine ground. The clinker finally pro- I 'duced is fine-ground to produce cement.

What I claim is p 1. .TI1BP1'QC8SS of produclng a cement and recovering ZlIlOf which comprlses commif nuting calcareous ore tailings carrying zinc With either a controlling the tempera-' oxid and zinc silicate, exposing suchtailings to a sintering heat and collecting the clinker and the fumiform zinc oxid produced.

. 2. The process of producing a cement and recovering zinc which comprises comminuting calcareous ore thefranklinite type, exposing such tailings j to a sintering heat and collecting the clinkerand the fumiform zinc oxid produced. i

3; The process of producing a cement and recovering zinc which comprises commi-' nuting calcareous ore tailings carrying zinc oxid-and zinc silicate, passing the commitailings from ores of.

nuted material down through a rotary kiln against opposed heating gases, finishing at a sintering heat, collecting the clinker produced and collecting the fumiform zincoxid prises comminuting a concentration product.

of franklinite ore, correcting the composi tion. by additions of components lacking to make a high grade cement, exposing the mixture to acalcining and a sintering heat and separately recovering the zinc oxid and clinker prpduced.

prises comminuting the final tailings from the concentration of franklinite ore, correct- 'ing the composition by addition of a concentration product carrying a'higher amount of silicates, exposing the mixture to a calcining and a sintering heat and separately-recovering the zinc oxid and clinker produced.

7. As a new composition of matter, a ee- I 6. In the recovery of zinc and the produc- N tion of a cement, the process which comment clinker having the approximate. composition of calcined manganiferous franklinite ore tailings, carrying a fraction of a per cent. of zinc oxid, being in theform of clinkered aggregates and upon comminution exhibiting setting roperties with water. In testimony whereo I aifix my signature in the presence of witnesses. I

ARTHUR, o. SPENCER. Witnesses JOHN H. SIGGERS, K. R MGELROY. 

